Ionic modulation and ionic coupling effects in MoS2 devices for neuromorphic computing

Abstract

Coupled ionic–electronic effects present intriguing opportunities for device and circuit development. In particular, layered two-dimensional materials such as MoS2 offer highly anisotropic ionic transport properties, facilitating controlled ion migration and efficient ionic coupling among devices. Here, we report reversible modulation of MoS2 films that is consistent with local 2H–1T′ phase transitions by controlling the migration of Li+ ions with an electric field, where an increase/decrease in the local Li+ ion concentration leads to the transition between the 2H (semiconductor) and 1T′ (metal) phases. The resulting devices show excellent memristive behaviour and can be directly coupled with each other through local ionic exchange, naturally leading to synaptic competition and synaptic cooperation effects observed in biology. These results demonstrate the potential of direct modulation of two-dimensional materials through field-driven ionic processes, and can lead to future electronic and energy devices based on coupled ionic–electronic effects and biorealistic implementation of artificial neural networks.

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Fig. 1: Electric field control of reversible 2H–1T′ phase transition in LixMoS2 films.
Fig. 2: 2H/1T′ phase composition tuning in LixMoS2.
Fig. 3: LixMoS2 film morphology changes caused by Li+ ion redistribution.
Fig. 4: Implementation of synaptic competition among LixMoS2 devices.
Fig. 5: Implementation of synaptic cooperation among LixMoS2 devices.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

The authors thank K. Sun and A. Hunter for their help with the TEM measurements, and W. Ma, S. Lee, Q. Cui, J. Guo and Y. Li for helpful discussions and their assistance during the experiments. This work was supported in part by the National Science Foundation through grant numbers ECCS-1708700 and CCF-1617315.

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X.Z. and W.D.L. designed the project and constructed the research frame. X.Z. and D.L. fabricated the devices and performed the measurements. X.Z., X.L. and W.D.L. analysed the experimental data. W.D.L directed the project. All authors discussed the results and implications and commented on the manuscript at all stages.

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Correspondence to Wei D. Lu.

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Supplementary Figures 1–27, Supplementary Notes 1,2, Supplementary References 1–9

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Zhu, X., Li, D., Liang, X. et al. Ionic modulation and ionic coupling effects in MoS2 devices for neuromorphic computing. Nature Mater 18, 141–148 (2019). https://doi.org/10.1038/s41563-018-0248-5

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